setup_color.py should not be executable, as it pollutes $PATH.

R=iannucci@chromium.org

Change-Id: Ieb9d76736203a346d8364c6c0448d9bb4391a3f7
Reviewed-on: https://chromium-review.googlesource.com/475832
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>